Many people that gave up their land lines, ported their numbers that they have for years, to the cell phones. The reverse lookups scan PUBLIC phone number data bases (which most landlines were public look ups).

And many of those data bases are pretty old, as any search on my cell phone number, says my number is AT&T (been T-Mobile since 2008) and that the name on the account, belongs to someone that had the number before I did, and I have had the number since 1992.